app.py

import fasttext
from fastapi import FastAPI, HTTPException, Depends
from fastapi.security import APIKeyHeader
from pydantic import BaseModel
from huggingface_hub import hf_hub_download
import os

app = FastAPI()

# API Key security – read from environment secret
API_KEY = os.getenv("INTERNAL_API_KEY")
if not API_KEY:
    raise RuntimeError("INTERNAL_API_KEY environment variable not set")
API_KEY_NAME = "X-Internal-API-Key"

api_key_header = APIKeyHeader(name=API_KEY_NAME, auto_error=False)

async def verify_api_key(api_key: str = Depends(api_key_header)):
    if not api_key or api_key != API_KEY:
        raise HTTPException(status_code=403, detail="Invalid API Key")
    return api_key

# Download the model (1.2 GB) only once when the Space starts
MODEL_PATH = hf_hub_download(
    repo_id="facebook/fasttext-language-identification",
    filename="model.bin"
)
model = fasttext.load_model(MODEL_PATH)

class TextInput(BaseModel):
    text: str

class DetectionResult(BaseModel):
    language: str      # e.g., "amh", "tir", "orm", "gaz", "eng"
    confidence: float
    raw_label: str     # e.g., "__label__amh_Ethi"

@app.post("/detect", response_model=DetectionResult)
async def detect_language(input: TextInput, _ = Depends(verify_api_key)):
    if not input.text or not input.text.strip():
        raise HTTPException(status_code=400, detail="Empty text")

    predictions = model.predict(input.text, k=1)
    raw_label = predictions[0][0].replace('__label__', '')
    confidence = float(predictions[1][0])
    # Extract base language code (e.g., "orm" from "orm_Latn")
    lang_code = raw_label.split('_')[0] if '_' in raw_label else raw_label

    return {
        "language": lang_code,
        "confidence": confidence,
        "raw_label": raw_label
    }

@app.get("/health")
async def health():
    return {"status": "ok"}